The present invention relates to a magnetoresistive effect type of head for detecting intensity of a magnetic field utilizing a resistive change according to the intensity of the magnetic field, and an information-reproducing system for reproducing information stored in a storage medium.
As computers have come into wide use, a lot of information is dealt routinely recently. Such information is stored in a storage medium with a large number of physical marks, and is reproduced by an information-reproducing system for reading those marks to produce an electric reproduction signal.
A hard disk device (HDD: Hard Disk Drive) is one of such an information-reproducing system and has aspects that it has a large storage capacity and an access time to information is fast. Generally, such a HDD is provided with a magnetic disk of which a surface is a recording medium made of a magnetic material and a reproducing head for reproducing information stored in the magnetic disk. The magnetic disk is magnetized in its surface for each minute area (one-bit area) in which one-bit of information is recorded in the form of a direction of magnetization of the one-bit area. The reproducing head is disposed close to the magnetic disk to output an electric reproduction signal according to a magnetic field generated from the one-bit area of the magnetic disk and thereby reproducing information recorded on the magnetic disk.
Currently, in many of the reproducing heads, which are loaded on the HDD, a signal is sent through a magnetoresistive effect type of head (MR head) which has a magnetoresistive effect element varying a resistance in accordance with an external magnetic field. The magnetoresistive effect element is utilized to generate a high output reproduction signal. However, every year a recording density of a magnetic disk is enhanced, and as the recording density is enhanced, a size of the respective one-bit area of the magnetic disk is reduced, and a magnetic field generated from the magnetization of the one-bit area is weakened. Thus, there is needed a head which outputs a large reproduction signal to such a weakened external magnetic field. As a head that outputs such a large reproduction signal, there is known a spin valve magnetoresistive head (SVMR head). Making the spin valve magnetoresistive head fit for practical use starts in earnest. Hereinafter, the spin valve magnetoresistive head is referred to as an SVMR head.
The SVMR head has a spin valve element consisting of a multi-layer film including a free magnetic layer varying in a direction of magnetization in accordance with an external magnetic field, a non-magnetic metal layer, a fixed magnetic layer fixed in a direction of magnetization, and an antiferromagnetic layer for fixing a direction of magnetization of the fixed magnetic layer. A sensing current conducts through the spin valve element. The spin valve element is one of the above-mentioned magnetoresistive effect elements. In the spin valve element, when the external magnetic field is varied, the free magnetic layer of the spin valve element is varied in a direction of magnetization, and a resistance is varied in accordance with a relative angle variation between a direction of magnetization of the fixed magnetic layer and a direction of magnetization of the free magnetic layer. Generally, efficiency of the resistive change of the magnetoresistive effect element according to the variation of the external magnetic field is expressed by a magnetoresistive rate RMR. The magnetoresistive rate RMR is defined by RMR=(xcfx81maxxe2x88x92xcfx810)/xcfx810. xcfx810 denotes a rate of the magnetoresistive effect element wherein the external magnetic field is not applied. xcfx81max denotes the maximum rate of the magnetoresistive effect element wherein the external magnetic field is applied. The spin valve element is large in the magnetoresistive rate, which brings about a large output change through the above-mentioned sensing current. Incidentally, hereinafter, the magnetoresistive rate is referred as MR rate.
As one way of providing higher output of the SVMR head, there is considered a reduction of the height of an element of the spin valve element. Reducing the height of an element of the spin valve element causes a sectional area of a conduction path for the sensing current to be reduced so that the resistive change xcfx81maxxcfx810 becomes large, while the MR rate is not increased. Thus, it is possible to obtain a large output of reproduction signal. However, a direction of magnetization of the fixed magnetic layer points to a direction of height of the spin valve element. Accordingly, a simple reduction of height of the spin valve element causes a demagnetizing field of the fixed magnetic layer to be enhanced so that fixing of the magnetization of the fixed magnetic layer is weakened, and as a result the direction of the magnetization is inclined with a discrepancy from the above-mentioned predetermined direction. This is associated with a problem that a waveform of the reproduction signal is distorted.
In order to weaken an influence of the demagnetizing field, there is known a spin valve element in which a fixed magnetic layer is constituted of a laminated ferrimagnetic film taking a three-layer structure of a first fixed magnetic layer indicative of ferromagnetism, a second fixed magnetic layer indicative of ferromagnetism and an opposite-parallel-coupling intermediate layer interposed between those first and second fixed magnetic layers, in which magnetizations of those fixed magnetic layers are coupled with each other in such a manner that those magnetizations are pointed in directions which are substantially parallel and mutually opposite. According to such a laminated ferrimagnetic film, the magnetizations of the first and second fixed magnetic layers come close to one another pointing in the opposite direction and running parallel. Thus, those magnetizations are kept being strongly fixed even if height in the element is reduced, so that a direction of the magnetization is stably maintained. In this manner, according to the SVMR head in which the laminated ferrimagnetic film is adopted in the fixed magnetic layer, it is possible to contribute to providing a higher output through reducing height in the element as mentioned above, while magnetization of the fixed magnetic layer is strongly fixed.
Further, there is known, other than the spin valve element in which the fixed magnetic layer is provided in form of the laminated ferrimagnetic film as mentioned above, a spin valve element in which a free magnetic layer is provided in form of a laminated ferrimagnetic film consisting of a first free magnetic layer, an opposite-parallel-coupling intermediate layer and a second free magnetic layer.
However, according to the SVMR head wherein the laminated ferrimagnetic layer is adopted for the free magnetic layer and the fixed magnetic layer, the laminated ferrimagnetic layer has, as mentioned above, two pieces of magnetization mutually pointed to the opposite directions, and a relative angle defined by a direction of magnetization of the free magnetic layer and a direction of magnetization of the fixed magnetic layer simultaneously takes two sorts of angle, for example, 0xc2x0 and 180xc2x0. For this reason, magnetoresistive effects for the two sorts of angle are mixed. This is associated with such a defect that it is easy that the MR rate is lowered.
In view of the foregoing, it is an object of the present invention to provide a magnetoresistive effect type of head that is high in the magnetoresistive rate (MR rate) while including the laminated ferrimagnetic film.
To achieve the above-mentioned object, the present invention provides a first magnetoresistive effect type of head having a magnetoresistive effect element offering a resistive change according to intensity of an external magnetic field, for detecting a magnitude of a resistance of the magnetoresistive effect element to detect intensity of a magnetic field, said magnetoresistive effect element consisting of a multi-layer film including a free magnetic layer varying in a direction of a magnetization in accordance with the external magnetic field and a fixed magnetic layer fixed in a direction of a magnetization, wherein
said free magnetic layer has a first free magnetic layer, a second free magnetic layer laminated at a position farther from the fixed magnetic layer as compared with the first free magnetic layer, and an opposite-parallel-coupling intermediate layer interposed between the first free magnetic layer and the second free magnetic layer, in which magnetizations of the first and second free magnetic layers are coupled with one another in such a manner that the magnetizations are pointed in directions which are substantially parallel and mutually opposite, and
said second free magnetic layer is formed with a material which is different from a material of said first free magnetic layer, and with a material in which an electron in said first free magnetic layer is subjected to an elastic scattering within said second free magnetic layer, within said opposite-parallel-coupling intermediate layer, and/or at the interface between said second free magnetic layer and said the opposite-parallel-coupling intermediate layer, said elastic scattering occurring at higher rate as compared with a case where said second free magnetic layer is formed with a material which is same as said first free magnetic layer.
In this manner, in the event that the second free magnetic layer is formed with a material wherein an electron is easy to be subjected to elastic scattering, the electron is hard to enter the second free magnetic layer, so that a magnetoresistive effect occurs mostly by a spin-dependent scattering of electrons in the first free magnetic layer and the fixed magnetic layer. Thus, as will be described latter in the preferred embodiment, MR rate of the magnetoresistive effect element is enhanced, and it is possible to obtain a magnetoresistive effect type of head capable of providing a higher output.
To achieve the above-mentioned object, the present invention provides a second magnetoresistive effect type of head having a magnetoresistive effect element offering a resistive change according to intensity of an external magnetic field, for detecting a magnitude of a resistance of the magnetoresistive effect element to detect intensity of a magnetic field, said magnetoresistive effect element consisting of a multi-layer film including a free magnetic layer varying in a direction of a magnetization in accordance with the external magnetic field and a fixed magnetic layer fixed in a direction of a magnetization, wherein
said free magnetic layer has a first free magnetic layer, a second free magnetic layer laminated at a position farther from the fixed magnetic layer as compared with the first free magnetic layer, and an opposite-parallel-coupling intermediate layer interposed between the first free magnetic layer and the second free magnetic layer, in which magnetizations of the first and second free magnetic layers are coupled with one another in such a manner that the magnetizations are pointed in directions which are substantially parallel and mutually opposite, and
said second free magnetic layer is formed with a material which is different from a material of said first free magnetic layer, and has a resistivity higher than that of said first free magnetic layer.
In this manner, in the event that the second free magnetic layer has a resistivity higher than that of the first free magnetic layer, the electron is hard to enter the second free magnetic layer, so that a magnetoresistive effect occurs mostly by a spin-dependent scattering of electrons in the first free magnetic layer and the fixed magnetic layer. Thus, as will be described later in the preferred embodiment, MR rate of the magnetoresistive effect element is enhanced, and it is possible to obtain a magnetoresistive effect type of head capable of providing a higher output.
In the above-mentioned second magnetoresistive effect type of head, it is preferable that second free magnetic layer has a resistivity not less than 200 xcexcxcexa9 cm.
As the resistivity of the first free magnetic layer and the opposite-parallel-coupling intermediate layer, similar to the resistivity of the free magnetic layer of the general magnetoresistive effect type of head, 50 xcexcxcexa9 cm or less is assumed. Electrons are particularly hard to enter the second free magnetic layer having the resistivity not less than 200 xcexcxcexa9 cm, which is higher as compared with this resistivity, that is, the resistivity of the free magnetic layer of the general magnetoresistive effect type of head, 50 xcexcxcexa9 cm or less.
To achieve the above-mentioned object, the present invention provides a third magnetoresistive effect type of head having a magnetoresistive effect element offering a resistive change according to intensity of an external magnetic field, for detecting a magnitude of a resistance of the magnetoresistive effect element to detect intensity of a magnetic field, said magnetoresistive effect element consisting of a multi-layer film including a free magnetic layer varying in a direction of a magnetization in accordance with the external magnetic field and a fixed magnetic layer fixed in a direction of a magnetization, wherein
said fixed magnetic layer has a first fixed magnetic layer, a second fixed magnetic layer laminated at a position farther from the free magnetic layer as compared with the first fixed magnetic layer, and an opposite-parallel-coupling intermediate layer interposed between the first fixed magnetic layer and the second fixed magnetic layer, in which magnetizations of the first and second fixed magnetic layers are coupled with one another in such a manner that the magnetizations are pointed in directions which are substantially parallel and mutually opposite, and
said second free magnetic layer is formed with a material which is different from a material of said first fixed magnetic layer, and with a material in which an electron in said first fixed magnetic layer is subjected to an elastic scattering within said second fixed magnetic layer, within said opposite-parallel-coupling intermediate layer, and/or at the interface between said second fixed magnetic layer and said the opposite-parallel-coupling intermediate layer, said elastic scattering occurring at higher rate as compared with a case where said second fixed magnetic layer is formed with a material which is same as said first fixed magnetic layer.
In this manner, in the event that the second fixed magnetic layer is formed with a material wherein an electron is easy to be subjected to elastic scattering, the electron is hard to enter the second fixed magnetic layer, so that a magnetoresistive effect occurs mostly by a spin-dependent scattering of electrons in the first fixed magnetic layer and the free magnetic layer. Thus, as will be described latter in the preferred embodiment, MR rate of the magnetoresistive effect element is enhanced, and it is possible to obtain a magnetoresistive effect type of head capable of providing a higher output.
To achieve the above-mentioned object, the present invention provides a fourth magnetoresistive effect type of head having a magnetoresistive effect element offering a resistive change according to intensity of an external magnetic field, for detecting a magnitude of a resistance of the magnetoresistive effect element to detect intensity of a magnetic field, said magnetoresistive effect element consisting of a multi-layer film including a free magnetic layer varying in a direction of a magnetization in accordance with the external magnetic field and a fixed magnetic layer fixed in a direction of a magnetization, wherein
said fixed magnetic layer has a first fixed magnetic layer, a second fixed magnetic layer laminated at a position farther from the free magnetic layer as compared with the first fixed magnetic layer, and an opposite-parallel-coupling intermediate layer interposed between the first fixed magnetic layer and the second fixed magnetic layer, in which magnetizations of the first and second fixed magnetic layers are coupled with one another in such a manner that the magnetizations are pointed in directions which are substantially parallel and mutually opposite, and
said second fixed magnetic layer is formed with a material which is different from a material of said first fixed magnetic layer, and has a resistivity higher than that of said first fixed magnetic layer.
In this manner, in the event that the second fixed magnetic layer has a resistivity higher than that of the first fixed magnetic layer, the electron is hard to enter the second fixed magnetic layer, so that a magnetoresistive effect occurs mostly by a spin-dependent scattering of electrons in the first fixed magnetic layer and the free magnetic layer. Thus, as will be described latter in the preferred embodiment, MR rate of the magnetoresistive effect element is enhanced, and it is possible to obtain a magnetoresistive effect type of head capable of providing a higher output.
In the above-mentioned fourth magnetoresistive effect type of head, it is preferable that second fixed magnetic layer has a resistivity not less than 200 xcexcxcexa9 cm.
As the resistivity of the first fixed magnetic layer and the opposite-parallel-coupling intermediate layer, similar to the resistivity of the free magnetic layer of the general magnetoresistive effect type of head, 50 xcexcxcexa9 cm or less is assumed. Electrons are particularly hard to enter the second fixed magnetic layer having the resistivity not less than 200 xcexcxcexa9 cm, which is higher as compared with this resistivity, that is, the resistivity of the free magnetic layer of the general magnetoresistive effect type of head, 50 xcexcxcexa9 cm or less.
To achieve the above-mentioned object, the present invention provides a fourth magnetoresistive effect type of head having a magnetoresistive effect element offering a resistive change according to intensity of an external magnetic field, for detecting a magnitude of a resistance of the magnetoresistive effect element to detect intensity of a magnetic field, said magnetoresistive effect element consisting of a multi-layer film including a free magnetic layer varying in a direction of a magnetization in accordance with the external magnetic field and a fixed magnetic layer fixed in a direction of a magnetization, wherein
said fixed magnetic layer has a hard magnetic layer laminated at a position farther from the free magnetic layer as compared with the fixed magnetic layer, and an opposite-parallel-coupling intermediate layer interposed between the fixed magnetic layer and the hard magnetic layer, in which magnetization of the fixed magnetic layer and magnetization of the hard magnetic layer are coupled with one another in such a manner that the magnetizations are pointed in directions which are substantially parallel and mutually opposite, and
said hard magnetic layer has a resistivity higher than that of said fixed magnetic layer.
In this manner, in the event that the hard magnetic layer has a resistivity higher than that of the fixed magnetic layer, the electron is hard to enter the hard magnetic layer, so that a magnetoresistive effect occurs mostly by a spin-dependent scattering of electrons in the free magnetic layer and the fixed magnetic layer. Thus, as will be described latter in the preferred embodiment, MR rate of the magnetoresistive effect element is enhanced, and it is possible to obtain a magnetoresistive effect type of head capable of providing a higher output.
In the above-mentioned fifth magnetoresistive effect type of head, it is preferable that second fixed magnetic layer has a resistivity not less than 200 xcexcxcexa9 cm.
As the resistivity of the first fixed magnetic layer and the opposite-parallel-coupling intermediate layer, similar to the resistivity of the fixed magnetic layer of the general magnetoresistive effect type of head, 50 xcexcxcexa9 cm or less is assumed. Electrons are particularly hard to enter the hard magnetic layer having the resistivity not less than 200 xcexcxcexa9 cm, which is higher as compared with this resistivity, that is, the resistivity of the fixed magnetic layer of the general magnetoresistive effect type of head, 50 xcexcxcexa9 cm or less.
To achieve the above-mentioned object, the present invention provides a first information-reproducing system, having a magnetic head for detecting magnetization of points in a magnetic storage medium storing information according to a direction of magnetization, said magnetic head being disposed coming closed to or contacting with the magnetic storage medium, for reproducing information according to magnetization of points in the magnetic storage medium detected by said magnetic head, wherein
said magnetic head has a magnetoresistive effect element offering a resistive change according to intensity of an external magnetic field, for detecting a magnitude of a resistance of the magnetoresistive effect element to detect intensity of a magnetic field, said magnetoresistive effect element consisting of a multi-layer film including a free magnetic layer varying in a direction of a magnetization in accordance with the external magnetic field and a fixed magnetic layer fixed in a direction of a magnetization, wherein
said free magnetic layer has a first free magnetic layer, a second free magnetic layer laminated at a position farther from the fixed magnetic layer as compared with the first free magnetic layer, and an opposite-parallel-coupling intermediate layer interposed between the first free magnetic layer and the second free magnetic layer, in which magnetizations of the first and second free magnetic layers are coupled with one another in such a manner that the magnetizations are pointed in directions which are substantially parallel and mutually opposite, and
said second free magnetic layer is formed with a material which is different from a material of said first free magnetic layer, and with a material in which an electron in said first free magnetic layer is subjected to an elastic scattering within said second free magnetic layer, within said opposite-parallel-coupling intermediate layer, and/or at the interface between said second free magnetic layer and said the opposite-parallel-coupling intermediate layer, said elastic scattering occurring at higher rate as compared with a case where said second free magnetic layer is formed with a material which is same as said first free magnetic layer.
The magnetic head of the first information-reproducing system corresponds to the first magnetoresistive effect type of head as mentioned above. According to this magnetic head, in a similar fashion to that of the first magnetoresistive effect type of head as mentioned above, MR rate of the magnetoresistive effect element is enhanced, and it is possible to obtain a magnetic head capable of providing a higher output.
Incidentally, there is considered an information-reproducing system in which the magnetic head of the first information-reproducing system is replaced by the magnetic head corresponding to the second magnetoresistive effect type of head. Thus, when the magnetic head corresponding to the second magnetoresistive effect type of head is adopted, in a similar fashion to that of the second magnetoresistive effect type of head as mentioned above, MR rate of the magnetoresistive effect element is enhanced, and it is possible to obtain an information-reproducing system capable of providing a higher output.
To achieve the above-mentioned object, the present invention provides a second information-reproducing system, having a magnetic head for detecting magnetization of points in a magnetic storage medium storing information according to a direction of magnetization, said magnetic head being disposed coming closed to or contacting with the magnetic storage medium, for reproducing information according to magnetization of points in the magnetic storage medium detected by said magnetic head, wherein
said magnetic head has a magnetoresistive effect element offering a resistive change according to intensity of an external magnetic field, for detecting a magnitude of a resistance of the magnetoresistive effect element to detect intensity of a magnetic field, said magnetoresistive effect element consisting of a multi-layer film including a free magnetic layer varying in a direction of a magnetization in accordance with the external magnetic field and a fixed magnetic layer fixed in a direction of a magnetization, wherein
said fixed magnetic layer has a first fixed magnetic layer, a second fixed magnetic layer laminated at a position farther from the free magnetic layer as compared with the first fixed magnetic layer, and an opposite-parallel-coupling intermediate layer interposed between the first fixed magnetic layer and the second fixed magnetic layer, in which magnetizations of the first and second fixed magnetic layers are coupled with one another in such a manner that the magnetizations are pointed in directions which are substantially parallel and mutually opposite, and
said second free magnetic layer is formed with a material which is different from a material of said first fixed magnetic layer, and with a material in which an electron in said first fixed magnetic layer is subjected to an elastic scattering within said second fixed magnetic layer, within said opposite-parallel-coupling intermediate layer, and/or at the interface between said second fixed magnetic layer and said the opposite-parallel-coupling intermediate layer, said elastic scattering occurring at higher rate as compared with a case where said second fixed magnetic layer is formed with a material which is same as said first fixed magnetic layer.
The magnetic head of the second information-reproducing system corresponds to the third magnetoresistive effect type of head as mentioned above. According to this magnetic head, in a similar fashion to that of the second magnetoresistive effect type of head as mentioned above, MR rate of the magnetoresistive effect element is enhanced, and it is possible to obtain a magnetic head capable of providing a higher output.
Incidentally, there is considered an information-reproducing system in which the magnetic head of the second information-reproducing system is replaced by the magnetic head corresponding to the fourth magnetoresistive effect type of head. Thus, when the magnetic head corresponding to the fourth magnetoresistive effect type of head is adopted, in a similar fashion to that of the fourth magnetoresistive effect type of head as mentioned above, MR rate of the magnetoresistive effect element is enhanced, and it is possible to obtain an information-reproducing system capable of providing a higher output.
To achieve the above-mentioned object, the present invention provides a third information-reproducing system, having a magnetic head for detecting magnetization of points in a magnetic storage medium storing information according to a direction of magnetization, said magnetic head being disposed coming closed to or contacting with the magnetic storage medium, for reproducing information according to magnetization of points in the magnetic storage medium detected by said magnetic head, wherein
said magnetic head has a magnetoresistive effect element offering a resistive change according to intensity of an external magnetic field, for detecting a magnitude of a resistance of the magnetoresistive effect element to detect intensity of a magnetic field, said magnetoresistive effect element consisting of a multi-layer film including a free magnetic layer varying in a direction of a magnetization in accordance with the external magnetic field and a fixed magnetic layer fixed in a direction of a magnetization, wherein
said fixed magnetic layer has a hard magnetic layer laminated at a position farther from the free magnetic layer as compared with the fixed magnetic layer, and an opposite-parallel-coupling intermediate layer interposed between the fixed magnetic layer and the hard magnetic layer, in which magnetization of the fixed magnetic layer and magnetization of the hard magnetic layer are coupled with one another in such a manner that the magnetizations are pointed in directions which are substantially parallel and mutually opposite, and
said hard magnetic layer has a resistivity higher than that of said fixed magnetic layer.
The magnetic head of the second information-reproducing system corresponds to the fifth magnetoresistive effect type of head as mentioned above. According to this magnetic head, in a similar fashion to that of the fifth magnetoresistive effect type of head as mentioned above, MR rate of the magnetoresistive effect element is enhanced, and it is possible to obtain a magnetic head capable of providing a higher output.
As mentioned above, according to the present invention, it is possible to provide a magnetoresistive effect type of head that is high in the magnetoresistive rate (MR rate) while including the laminated ferrimagnetic film.